Abstract: Objective To understand the forensic practice of DNA profiling from minimal amount of DNA.Methods Serial dilutions of DNA were amplified with the PowerPlex TM 16System Kit,then the genotyping of short tandem repeat(STR)was performed by ABI377DNA automated Sequencer.Results When the mount of DNA template was less than250pg,allelic drop-out apparently occurred at several loci.Other disturbed peaks,such as artefact bands and imbalanced heterozygote,also presented.Conclusion The anomalous results may result in incorrect genotyping.Careful and comprehensive considerations are needed to interpret the STR profile of minute DNA.

Key words: short tandem repeats, low copy number DNA, forensic medicine, genotype